Blechnum occidentale (palm fern)

Pictures

Picture	Title	Caption	Copyright
Title Habit Caption Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit. Honokowai Ditch Trail, Maui, Hawaii, USA. June 2010. Copyright ©Forest & Kim Starr-2010 - CC BY 3.0	Habit	Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit. Honokowai Ditch Trail, Maui, Hawaii, USA. June 2010.	©Forest & Kim Starr-2010 - CC BY 3.0
Title Habit Caption Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit. Waikapu Valley, Maui, Hawaii, USA. April, 2012. Copyright ©Forest & Kim Starr-2012 - CC BY 3.0	Habit	Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit. Waikapu Valley, Maui, Hawaii, USA. April, 2012.	©Forest & Kim Starr-2012 - CC BY 3.0
Title Habit Caption Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit and habitat. Honokowai Ditch Trail, Maui, Hawaii, USA. June 2010. Copyright ©Forest & Kim Starr-2010 - CC BY 3.0	Habit	Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit and habitat. Honokowai Ditch Trail, Maui, Hawaii, USA. June 2010.	©Forest & Kim Starr-2010 - CC BY 3.0
Title Habit Caption Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit. Honokowai Ditch Trail, Maui, Hawaii, USA. June 2010. Copyright ©Forest & Kim Starr-2010 - CC BY 3.0	Habit	Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit. Honokowai Ditch Trail, Maui, Hawaii, USA. June 2010.	©Forest & Kim Starr-2010 - CC BY 3.0
Title Fronds Caption Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit, showing fronds. Honokowai Ditch Trail, Maui, Hawaii, USA. June 2010. Copyright ©Forest & Kim Starr-2010 - CC BY 3.0	Fronds	Blechnum occidentale (palm fern, catalogued as B. appendiculatum); habit, showing fronds. Honokowai Ditch Trail, Maui, Hawaii, USA. June 2010.	©Forest & Kim Starr-2010 - CC BY 3.0
Title Sori Caption Blechnum occidentale (palm fern, catalogued as B. appendiculatum); sori. Kula Botanical Garden, Maui, Hawaii, USA. March 2011. Copyright ©Forest & Kim Starr-2010 - CC BY 3.0	Sori	Blechnum occidentale (palm fern, catalogued as B. appendiculatum); sori. Kula Botanical Garden, Maui, Hawaii, USA. March 2011.	©Forest & Kim Starr-2010 - CC BY 3.0
Title Sori Caption Blechnum occidentale (palm fern, catalogued as B. appendiculatum); sori. West Maui, Maui, Hawaii, USA. February 2009. Copyright ©Forest & Kim Starr-2009 - CC BY 3.0	Sori	Blechnum occidentale (palm fern, catalogued as B. appendiculatum); sori. West Maui, Maui, Hawaii, USA. February 2009.	©Forest & Kim Starr-2009 - CC BY 3.0

Identity

Preferred Scientific Name

• Blechnum occidentale L.

Preferred Common Name

• palm fern

Other Scientific Names

• Blechnum appendiculatum Willd.
• Blechnum extensum Fée
• Blechnum glandulosum Kaulf. ex Link
• Blechnum glandulosum var. distans (C. Presl) C. Chr.
• Blechnum helveolum Fée
• Blechnum meridionale C. Presl
• Blechnum mucronatum Fée
• Blechnum occidentale var. intermedium (Link) E. Fourn.
• Blechnum occidentale var. lacerata Rosenstock
• Blechnum occidentale var. pubirhachis Rosenstock

International Common Names

• English: hammock fern

Local Common Names

• USA: New World midsorus fern

Summary of Invasiveness

B. occidentale is a medium sized fern, native to the Americas, that has become naturalized in Hawaii following escape from cultivation. Preferring shady conditions in mesic forests, particularly on rocks or rocky substrates, and being able to survive periods of drought, it produces sporophytes that can be long-lived and spread asexually by branching or budding. It can form large clonal colonies that suppress native plants, and is listed as one of the species causing habitat degradation and impacting endangered native plants in Hawaii. The large populations form mats effectively preventing the germination and growth of native species (Wilson, 1996). 

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Pteridophyta
•             Class: Pteridopsida
•                 Family: Blechnaceae
•                     Genus: Blechnum
•                         Species: Blechnum occidentale

Notes on Taxonomy and Nomenclature

The Blechnaceae is a family of 24 genera and 265 species (Gasper et al., 2016a; PPG I, 2016).The family has centres of diversity and endemism in the Neotropics and Australasia/Oceania, with a predominance of species and genera in the southern hemisphere (Gasper et al., 2016a). The genus Blechnum s.s. includes 30 species (PPG I, 2016). Most species are neotropical, with a few in southern Africa (Gasper et al., 2016a).

Blechnum appendiculatum was described by Carl Ludwig von Willdenow in 1810. The species epithet appendiculatum comes from the Latin appendicular, diminutive of appendix, meaning small appendages or projections, and atus, indicating possession. This possibly refers to the short glandular hairs on the rachises (Palmer, 2003). B. appendiculatum has been treated both as a separate species, and as an infraspecific taxon within, B. occidentale. Mickel and Smith (2004) noted that morphological differences between B. appendiculatum and B. occidentale (sensu stricto) “appear correlated with differences in elevation and pubescence, and there are relatively few specimens that are difficult to place in one species or the other.” In the most recent treatment of the B. occidentale group, however, Dittrich et al. (2015) found “a nearly continuous gradation in specimens from glabrous to few hairs to many hairs, indicating that this can be treated as the same taxon without any discontinuity between these variations”. This datasheet follows Dittrich et al. and treats B. occidentale as the accepted name, with B. appendiculatum as a synonym.

Description

The following description is from Dittrich et al. (2015): Plants terrestrial, rarely epipetric; rhizomes erect to decumbent, stoloniferous, the scales mostly bicolorous, linear-lanceolate or narrowly triangular, with a dark central stripe, 3.5–8.0 × 1.0–1.9 mm at base, margin entire; fronds monomorphic, 12.9–71.9 cm long; stipes 3.2–34.3 cm long, 1.5–2.1 mm diam., espcially at the base with tan, concolorous scales, the margin predominantly entire, with few denticles; blade 9.7–37.6 × 2.2–19.8 cm, ovallanceolate, ovate or deltoid, papyraceous to subcoriaceous, truncate at base, without vestigial pinnae, sometimes the pair of proximal pinnae slightly smaller than those immediately above, tapered toward apex, pinnate at base, pinatissect toward apex, glabrous or with multicellular trichomes abaxially on the veins; rachis glabrous or with multicellular, tan, hyaline trichomes; pinnae 10–27 pairs, 1.3–11.0 × 0.8–1.6 cm, reflexed or patent (basal ones), patent or ascending (median ones) or ascending (apical ones), sessile (basal ones), partially (median ones) or fully adnate (apical ones), falcate, apex acute, cuneate or mucronate, glabrous or rarely with trichomes on abaxial costa similar to those of abaxial rachis, basal ones acroscopically auriculate, the auricles usually overlapping the rachis, margins finely denticulate, but often slightly revolute and appearing entire; veins free, simple or 1–4(–5)-bifurcate, with clavate ends before the margin.

Plant Type

Distribution

B. occidentale is currently found in the Americas, from Texas and Florida in the USA, down as far south as Argentina and Paraguay in South America, and including some islands in the Caribbean (Dittrich et al., 2015; USDA-ARS, 2015). It is introduced and invasive in Hawaii (PIER, 2015). While USDA-ARS (2015) lists it as native throughout its range in the Americas, Seigler and Lockwood (1975) suggested that the USA populations had probably arisen from spores blown by the wind from Mexico or the West Indies. Diggs and Lipsocmb (2015) list it as rare and with limited distribution in Texas.

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

According to Palmer (2003), B. occidentale was first collected in Hawaii in 1918 having escaped from gardens. It has spread extensively to other parts of Hawaii, and is a clonal naturalized species. 

Habitat

In its native habitat, B. occidentale inhabits the interior of forests, most often growing along forest edges, trails, roads and rarely on rocks near streams (Dittrich et al., 2015). It occurs between 40 and 1600 m, and is present in seasonal deciduous and semideciduous forests, dense and mixed humid forests.

In Hawaii, large colonies are formed by clonal plants in closed-canopy mesic forests in all but the most extreme habitats at 30-1560 m in all islands (Palmer, 2003). Wilson (1996) reported it as weedy along trail sides, stream banks, forested slopes, and gulches on all islands, often growing in solid stands. It is common over rocks and rocky substrates, and in Texas it is found in granite crevices (Diggs and Lipscomb, 2015). 

Habitat List

Biology and Ecology

Adult ferns produce sporangia on the underside of the leaves and from these spores are expelled which, when they find a suitable habitat, develop into gametophytes. These form antheridia that produce many sperm and archegonia that produce a single ovum. Once maturation occurs, and in the presence of a thin film of water on the underside of the gametophyte, the sperm actively swim towards the ovum and fertilise it. Mechanisms prevent self-fertilization. The fertilized ovum now has two set of chromosomes and develops into a sporophyte. In Blechnum spp., the sporophytes can be long-lived and spread asexually by producing stolons that bud off new plants thereby forming large colonies (Palmer, 2003).

B. occidentale adapts to disturbance, is environmentally versatile, and thrives under drought conditions (Weller et al., 2011). 

Climate

Means of Movement and Dispersal

The spores can be dispersed by wind, and probably by water (PIER, 2015). Diggs and Lipscomb (2015) quote Seigler and Lockwood (1975) as suggesting that populations in the USA have probably arisen from spores blown by the wind from Mexico or the West Indies.

Pathway Vectors

Impact Summary

Environmental Impact

All the reports for negative environmental impact of this fern come from Hawaii, where it is an introduced species which competes against a number of native plants. B. occidentale forms thick mats that prevent establishment of seeds and spores of other plants (Wilson, 1996). Weller et al. (2011) report that B. occidentale increased in percentage cover during a drought period when native ferns decreased substantially. It competes with a number of native fern species, having particular impact on the rare genus Diellia (Palmer, 2003). Aguraiuja et al. (2004), for example, reported that on Kauai a site investigated for Diellia pallida was completely overgrown by Erigeron karvinskianus and B. occidentale. A review of the endangered Diellia erecta (US Fish and Wildlife Service, 2007) reports competition with invasive species including B. occidentale as a threat to the species. In IUCN assessments of the critically endangered fern Asplenium diellaciniatum (Kishida and Wood, 2015) and the endangered plant Cyrtandra heinrichii (Lorence and Edmonds, 2015), both found on Kauai Island in the Hawaiian Island chain, B. occidentale is listed as one of the alien species causing habitat degradation. The fern is also listed as degrading habitat for Nototrichium humile (US Fish and Wildlife Service, 2006).

Risk and Impact Factors

Impact mechanisms

• Competition

Impact outcomes

• Ecosystem change/ habitat alteration
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

Invasiveness

• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Is a habitat generalist
• Proved invasive outside its native range
• Reproduces asexually
• Tolerant of shade

Similarities to Other Species/Conditions

B. occidentale is close to B. austrobrasilianum and B. laevigatum. It is also similar to the hybrids B. × caudatum and B. × leopoldense. A key to identification is given in Dittrich et al. (2015).

Prevention and Control

Aguilar-Dorantes et al. (2015) report that glyphosate inhibits spore germination of B. occidentale even at low concentrations. The herbicide also killed the fern at all green life stages at most concentrations tested. However, herbicides should be used with care as associated plant species would also be affected. Mechanical control is likely to be ineffective given vegetative reproduction via stolons (PIER, 2015).

References

Aguilar-Dorantes K, Mehltreter K, Mata-Rosas M, Vibrans H, Esqueda-Esquivel V, 2015. Glyphosate susceptibility of different life stages of three fern species. American Fern Journal, 105(3):131-144. http://www.bioone.org/loi/amfj

Aguraiuja R, Moora M, Zobel M, 2004. Population stage structure of Hawaiian endemic fern taxa of Diellia (Aspleniaceae): implications for monitoring and regional dynamics. Canadian Journal of Botany, 82(10):1438-1445.

Andrews SB, 1990. Ferns of Queensland., Australia: Queensland Dept. of Primary Industries, 427 pp.

Clark M, 2015. Asplenium dielpallidum. The IUCN Red List of Threatened Species, 2015(e.T78774640A78774709). http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T78774640A78774709.en

Diggs G, Lipscomb B, 2015. Ferns of Texas. http://ferns.brit.org/

Dittrich VAO, Salino A, Monteiro R, 2015. The Blechnum occidentale (Blechnaceae, Polypodiopsida) species group in southern and southeastern Brazil. Phytotaxa, 231(3):201-229.

Gasper AL, Almeida TE, Dittrich VAO, Smith AR, Salino A, 2016. Molecular phylogeny of the fern family Blechnaceae (Polypodiales) with a revised genus-level treatment. Cladistics. DOI: 10.1111/cla.12173

Gasper AL, Dittrich VAO, Smith AR, Salino A, 2016. A classification for Blechnaceae (Polypodiales: Polypodiopsida): new genera, resurrected names, and combinations. Phytotaxa, 275(3):191-227.

Kishida W, Wood K, 2015. Asplenium diellaciniatum. The IUCN Red List of Threatened Species, e.T80229055A80229060. http://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T80229055A80229060.en

Lorence DH, Edmonds M, 2015. Cyrtandra heinrichii. The IUCN Red List of Threatened Species, e.T80231759A80231775. http://dx.doi.org/10.2305/IUCN.UK.2015- 4.RLTS.T80231759A80231775.en

Mickel JT, Smith AR, 2004. The pteridophytes of Mexico. New York, USA: New York Botanical Garden.

Missouri Botanical Garden, 2015. Tropicos database. St. Louis, Missouri, USA: Missouri Botanical Garden. http://www.tropicos.org/

Palmer DD, 2003. Hawaii's Ferns and Fern Allies. Honolulu, Hawaii, USA: University of Hawaii Press, 324 pp.

PIER, 2015. Pacific Islands Ecosystems at Risk. Honolulu, USA: HEAR, University of Hawaii. http://www.hear.org/pier/index.html

PPGI, 2016. A community-derived classification for extant lycophytes and ferns. Journal of Systematics and Evolution, 54(6):563-603.

Seigler DS, Lockwood TE, 1975. Blechnum occidentale new to Texas. American Fern Journal, 65:96.

The Plant List, 2013. The Plant List: a working list of all plant species. Version 1.1. London, UK: Royal Botanic Gardens, Kew. http://www.theplantlist.org

US Fish and Wildlife Service, 2006. 5-year review, Nototrichium humile. 11 pp. http://ecos.fws.gov/docs/five_year_review/doc1857.pdf

US Fish and Wildlife Service, 2007. 5-year review, Diellia erecta. 9 pp. http://www.fws.gov/ecos/ajax/docs/five_year_review/doc2466.pdf

USDA-ARS, 2015. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx

Weller SG, Cabin RJ, Lorence DH, Perlman S, Wood K, Flynn T, Sakai AK, 2011. Alien plant invasions, introduced ungulates, and alternative states in a mesic forest in Hawaii. Restoration Ecology, 19(5):671-680. http://onlinelibrary.wiley.com/doi/10.1111/j.1526-100X.2009.00635.x/full

Wilson KA, 1996. Alien ferns in Hawaii. Pacific Science, 50(2):127-141.

Contributors

29/02/16 Original text by:

Emma Thompson, Egham, CABI

Distribution Maps

• = Present, no further details
• = Evidence of pathogen
• = Widespread
• = Last reported
• = Localised
• = Presence unconfirmed
• = Confined and subject to quarantine
• = See regional map for distribution within the country
• = Occasional or few reports

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